Wildfires often erupt in remote areas having difficult terrain. Conditions such as high winds and dry weather may also cause a fire to become very large, very quickly resulting in an out of control fire that threatens woodland resources and developed areas alike. In order to combat wildfires under such conditions firefighting aircraft, also known as airtankers and water bombers, are often employed. The speed and capacity of firefighting aircraft make them an important tool in fighting larger, out of control fires. Particularly, where it is time consuming or unsafe to deploy firefighters and equipment on the ground. Firefighting aircraft can quickly deliver large quantities of fire retardant or water to an area to help control fires.
The density of retardant delivered to a given area of terrain is often referred to as the coverage level rating. Coverage level ratings range from 1 to 8, which are expressed in gallons of retardant per hundred square feet. For example, a coverage level rating of 4 corresponds to 4 gallons of retardant per hundred square feet. Depending on the desired coverage level the required fire retardant flow rate discharged from a firefighting aircraft can reach 2000 gallons per second.
Conventional firefighting aircraft include a tank for carrying water or retardant and doors or gates that open to allow the payload to discharge onto or in advance of the flames. Traditional retardant delivery systems rely on gravity to propel the retardant through the gates. Accordingly, large gates are required to allow the retardant to flow from the aircraft at a sufficient rate to meet the higher coverage level ratings. With conventional firefighting aircraft the gates simply open and discharge the retardant all at once. The pilot must therefore compensate for the speed and altitude of the aircraft as well as the discharge characteristics of the delivery system in order to provide the desired coverage level in the desired area.
The payload of a typical firefighting aircraft is in the neighborhood of 20,000 pounds of retardant or water. In order to support the weight of the retardant against the gates substantial opening/closing mechanisms are required. Also, traditional opening/closing mechanisms are located inside the tank in order to allow for support struts along the length of the gates. This configuration has the disadvantage of interfering with the flow of retardant through the gates. Furthermore, typical retardant formulations include components that may be corrosive to the supports and mechanisms that operate the gates, such that over time the supports and or mechanisms may fail or at least require excessive maintenance.
Accordingly, there is a need for an aerial retardant delivery system that can assist the pilot in safely delivering a desired coverage level to an area of terrain threatened by wildfire. There is a still further need for a retardant delivery system gate opening/closing mechanism that is configured for improved discharge characteristics as well as gate mechanism reliability and ease of maintenance.